I think he is saying, that hes concerned about the rumor of duplicate content and is afraid of losing any rankings he currently has.

Don't worry about the duplicate content.
as long as you build a sitemap, use robots.txt,
make sure you have the right codes in your .htaccess
Seo your content, you'll also need to promote it and get it indexed.
use ubl(dot)org to help get your new ecommerce mobile website listed in mobile devices and directories, and Gps locations & your website then is indexed as a mobile site.

Hope that helps. The above stuff is just the basics,
but helps to get you going in the right direction.

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